(a) Field of the Invention
The invention relates to the preparation and use of injectable self-forming mineral-polymer hybrid compositions for repairing, replacing or therapeutically treating tissues and body parts. More particularly, the present invention proposes self-gelling mineral-polymer hybrid formulations. More specifically, the present invention comprises self-gelling mineral-polymer hybrid formulations that comprises osteoconductive or osteoinductive agents, drugs or therapeutic and/or healing-accelerator components.
(b) Description of Prior Art
A large quantity of bio-materials have been introduced for hard-tissue repair and formation, including natural or synthetic materials, pure organic or inorganic materials, and organo-inorganic biohybrid or hybrid materials.
Conductive hard-tissue implants are passive bio-materials that provide a matrix to favor and support a new hard-tissue ingrowth and repair. They generally do not provide any osteogenesis property, in the meaning that such materials do not supply, by themselves, any osteogenesis or hard-tissue inductive factors, or any hard-tissue healing accelerators. Conductive structures have typically to favor the own ingrowth and reorganization of hard-tissues (Ex: osteoconductive materials).
The main constituent of hard-tissues is biological apatite that is commonly found in bone and teeth (65-98%). Calcium and phosphate ions are commonly contained in body fluids and mineral contents of hard tissues, including bones, dentine and dental enamel. They may also additionally contain other constituents such as carbonates, magnesium or sodium. Hydroxyapatite is generally recognized as being a calcium phosphate material with a crystal structure very close to biological apatite. Calcium phosphates, and some other ceramics, were found to be very useful biocompatible materials for hard-tissue repair. Today, a large family of ceramic bio-materials having different forms is available for repairing hard-tissues, and includes calcium phosphates, calcium carbonates, bioglasses and pure natural minerals.
Bone Repair and Formation
Conductive matrices for hard-tissue repair are designed to provide adequate compositions and architectures that favors the ingrowth of hard-tissue by its own. These matrices are inserted into a defect, thus contacting mature hard-tissue cells that are capable of invading the repairing matrix and forming mineral networks to complete tissue ingrowth. Typical examples are generally related to osteoconductive materials for bone tissues.
Conductive hard-tissue implants have received a considerable attention, particularly in bone surgery. Grafting materials for defect filling and bone repair include autografts, xenografts, demineralized bone matrix, porous ceramics such as calcium phosphates, calcium carbonates, coral, nacre, bioglasses, organic matrices (polymers, collagen and other biological macromolecules) as well as organo-inorganic biohybrid or hybrid materials such as organo-apatites.
Implants for filling and repairing defects are currently solids, sometimes gels and hydrogels that enable the ingrowth and conduction of the hard-tissue. Porous or plain solids may be used. Plain solid implants stimulate hard-tissue ingrowth through their own resorption. Porosity may be inherent to the material architecture (true porosity), or be interstitial.
Calcium phosphates have been the preferred bone bio-materials. In a large number of animal and human studies, they have been shown to be biocompatible, and bone growth promoters. Targeted calcium phosphate ceramics are tricalcium phosphates, amorphous calcium phosphate, octacalcium phosphate, and apatitic compounds. Hydroxyapatite [Ca10(PO4)6(OH)2], calcium-deficient apatite, fluorinated apatite [Ca10(PO4)6F2], and carbonated apatite [Ca10-xHax(PO4)6-x(CO3)x(OH)2] are the most representative apatitic compounds. Synthetic or sintered apatites may be prepared.
Most calcium phosphate ceramics are prepared as granules or block materials. Block materials can be prepared with various geometries such as rods, cylinders, rectangular shapes, etc. However, ceramic blocks must be re-shaped before implantation to fit exactly the defect size and geometry, which makes heavier and longer the handling and clinical application. Furthermore, calcium phosphate blocks are very brittle and difficult to shape, and consequently the interface between the bone tissue and ceramic implant is not perfectly continuous which may impair the osteoconduction efficiency. Calcium phosphate granules are currently produced with a wide size distribution, and available from 10 microns to 2.5 mm, but preferably used with a size between 90 and 400 microns. Granules can be injected, or at least administered through less invasive techniques, so as to fulfill the tissue defect. But granules have a mobility problem in situ, which limits their use and efficiency.
Ceramics such as calcium carbonates, coral or nacre are equally proposed under granular or block form, and present similar problems. Bioglasses are generally under granular or microspheric form (Bioglass®, USBio-materials; Biogran®, Orthovita; Perioglass®).
Typical commercial ceramic materials used as osteoconductive materials are for example apatite such as SurgiBone® (Unilab), Osteogen® HA Resorb (Impladent), Periograf®, Alveograft®, ProOsteon® (Interpore), Cerapatite® (Ceraver-Osteal), Ossatite® (MCP), Synatite® (SBM), Ceros®, Interpore® 200 (Interpore), OrthoMatrix™ HA-1000™ and HA-500™, Bio-Oss® (Osteohealth), Calcitite 2040®, Ceros 80® (Matthys), Durapatite®, Apafil-G® (Biomat), HAP Coralina®, Endobon® (Merk), Pyrost® (Osteo), or tricalcium phosphate such as Ceros 82®, Synthograft®, Bioresorb® (SBM), Calciresorb® (Ceraver-Osteal), or a mixture of hydroxyapatite and tricalcium phosphate (biphasic calcium phosphate) such as Triosite® (Zimmer), Ceraform® (Teknimed), Eurocer® (Bioland), BCP® (Bioland), Ostilit® (Howmedica), or coral such as BioCoral® (Inoteb).
Collagen, a component of soft- and hard-tissues, and Bone Demineralized Matrix (BDM) are the current organic materials for filling hard-tissue defects. Collagen was associated with mineral to form hybrid materials such as Collagraft® (NeuColl), Cerapatite-Collagen® (Ceraver-Osteal), Ossatite® composite (MCP) or Collapat® (Osteo).
Polymeric materials such as polylactic acid, polyglycolic acid, polylactic-co-glycolic acid microspheres, and the like, were also proposed for bone defect filling and repair, but are less current than calcium phosphate granular materials. One new development is Immix® (Osteobiologics) bone grafting material based on polylactic acid/glycolic acid (PLA/GA).
Osteoinduction
Osteogenesis factors are generally supplied by surrounding living tissues and blood supply in the vicinity of the hard-tissue implant. It would be highly desirable to propose a hard-tissue repair matrix that combines the ingrowth promotion of newly-formed hard-tissue tissue and the inductive action, for example, an implant material that allows osteoconduction and osteoinduction. The exact mechanism of hard-tissue formation is complex and not perfectly understood, but it is clear that a certain number of biochemical factors are involved in hard-tissue formation and mineralization. Repair of hard-tissues is induced by the maturation of progenitor cells into the expected functional tissue cells. For bone, osteogenesis is reached when osteoprogenitor cells are converted into bone cells that are active to form mineralization and bone tissues. It can be stated that osteogenesis can be obtained in situ through different actors: a) the osteoprogenitor cells that once converted will form bone repairing-forming cells; b) the inductive biochemical environment that will stimulate the conversion and maturation of osteoprogenitor cells and modulate the bone formation and repair response; and c) the conductive bone repairing matrix that will support the formation of new bone tissues and mineralized networks.
Osteogenic stimulation can be first elicitated by bone progenitor cells (osteoprogenitors). Marrow Stroma Cells (MSCS) are recognized as being the precursor cells of hard and connective tissues. Hematopoietic stem cells from bone marrow are also providers of osteoprogenitor cells and promoters of osteogenesis. The injection of bone marrow preparations, with or without carriers, has been described to stimulate osteogenesis and bone repair. The ability of bone marrow to form bone is well-known, and clinically used. Administration of bone marrow through demineralized bone matrix, collagen or hydroxyapatite materials is also observed for repairing bone defects. Retransplantation of MSCs into poorly healing bone is currently viewed as potentially enhancing the repair process.
Cytokines are bioactive proteins that act on cells adjacent to the cell where is it elaborated. Cytokines and bone proteins have been intensively studied in terms of inductive or healing accelerating effects on hard-tissues, and especially on bone, including “bone-derived osteogenesis proteins” (bOP), “bone morphogenic proteins” (BMP) and “growth and differentiation factors” (GDF). BMPs and GDFs from the Transforming Growth Factor-beta gene super-family have been extensively investigated and used for bone formation and repair. Transforming Growth Factor-beta (TGF-beta), Fibroblast Growth Factors (FGF, a-b), and Platelet-Derived Growth Factors (PDGF, A-B) have been proven useful during fracture healing, thus acting at different steps of fracture healing, including the initial injury response, the intramembraneous ossification, the chondrogenesis or the endochondreal ossification.
Commercial developments in osteoinductive or osteoregulating agents comprise rhBMP-2 (Genetic Institute), Ne-Osteo (Sulzer Orthopedics, Biologics), OP-1 (Stryker Biotech), Indian Hedgehog inducing molecule (Ontogeny) and Plasmid DNA (Matrigen).
One key-step in using biological inductive actors is the clinical administration and dosing. Furthermore, bio-materials development for reaching minimally-invasive administration, easiness of application and optimal induction-conduction of hard-tissues is still running, and is a matter of great interest.
The administration to bone of DNA or genetically-modified cells such as MSCs are potential avenues to treat durably hard-tissue deficiencies. When released in-situ, DNA is taken up by the granulation cells which become drug dispensing agents and stimulate formation of hard-tissues. DNA can be dispensed during the granulation component of healing, thus enabling the control of the protein expression for days and weeks and allowing a control of the sequence of events that normally take place in hard-tissue formation. It may be particularly attractive for patients with hard-to-heal fractures or imperfect bone healing. Genetic reprogramming of MSCs so as to express specific proteins may be used therapeutically for hard-tissues as well as for other connective tissues as in the case of deficiencies in circulating proteins. Re-transplantation of genetically-modified MSC cells is a way to control or cure diseases at the genetic level.
Diseases and/or deficiencies associated to hard-tissues may necessitate both a filling, a repair and a local therapeutic treatment, e.g. a partial resection of bone tissue and/or a localized application of therapeutics. Antibiotic, anti-inflammatory, anticancer, antiviral, antimicrobial and/or antibacterial agents may be administrated to hard-tissue sites, e.g. anticancer/antitumor agents introduced in a defect surgically made for resecting a bone tumor. The agent will act so as to prevent or control the recurrence of the tumor in bone.
Injectable Bone Substitutes
Injectable systems were introduced for healing, repair and formation of bone through less invasive and traumatic techniques such as percutaneous methods. Different bio-material concepts have been proposed, and may be classified as follows: a) the pharmaceutical vehicles for bone treatment (Ex: gels); b) the hybrid bone filling/grafting materials (Ex: injectable ceramic/polymer composites); and c) the self-setting bone substitute (Ex: injectable bone cements).
Hyaluronic acid-based gels were proposed for delivering growth factors (OssiGel™) such as basic FGF, thus acting to accelerate fracture healing. Matrigel and Collagen gels were introduced to support and deliver DNA (gene therapy) for hard-tissues (Matrigen™). Those materials are pure organic vehicles, with no mineral content, and no self-forming action.
Particulate solids made of polymers, ceramics or inorganics are currently known as potential injectable materials for defect filling, and to some extent, carrying and delivering systems for soft- and hard-tissues. But injectable granular materials are highly mobile causing problems in situ.
Injectable hybrid bone materials were proposed from granular solids such as, and particularly with, calcium phosphate ceramics dispersed and homogenized in an organic fluidic matrix. Blood and physiological fluid were currently used as the carrier, but do not form really a matrix. Biological sealants such as the fibrin glue were proposed as a matrix to develop a ceramic composite bone material (Sedel et al., J. Biomed. Mat. Res. (Appl. Biomat.), 43:38-45, 1998; and Wilson et al., Bio-materials, 15:601-608, 1993). Poly(propylene fumarate) [PPF] based matrix was also promoted to carry ceramics and form bone composite materials (Mikos et al., J. Biomed. Mat. Res., 44:314-321, 1999). Gelatin was used similarly in Ossatite® (Medical Calcium Phosphate Laboratories, France) injectable bone product (Griffet et al., Bio-materials, 20:511-515, 1999). Cellulosics, and especially cellulosic ethers such as hydroxypropyl methylcellulose (HPMC), are currently investigated as a promising carrier/matrix in injectable bone composite materials (Daculsi et al., J. Biomed. Mat. Res., 47:28-35, 1999; Dupraz et al., Bio-materials, 20:663-673, 1999; and Grimandi et al., J. Biomed. Mat. Res., 39:660-666, 1998). Daculsi et al. (U.S. Pat. No. 5,717,006) was promoting cellulosics for processing composite bio-materials that contain 40 to 75% by weight of a mineral content. This mineral content was a blend of hydroxyapatite [Ca10(PO4)6(OH)2] and beta-tricalcium phosphate, or calcium titanium phosphate [Ca(Ti)4(PO4)6].
Injectable hybrid compositions for hard-tissues were proposed (U.S. Pat. No. 5,352,715), where a ceramic matrix comprising particles between 50 and 250 microns was dispersed in the fluid carrier. Fluid carrier and nonceramic compounds were selected from collagen, polyethylene glycol, glycerol or succinylated collagen. Collagen was promoted in many systems (U.S. Pat. No. 4,795,467; and U.S. Pat. No. 5,071,436). Ceramic was generally calcium phosphates such as apatites or tricalcium phosphate (U.S. Pat. No. 6,027,742). Bioactive agents were potentially incorporated in the hybrid composition. Another injectable system was presented by Hench et al. (U.S. Pat. No. 5,840,290), consisting in a suspension of bioglasses in a Dextran aqueous solution. Bioglass particles were 90 to 250 microns in size, consisting in 45S5 (Orthovita) glass composition. Fibrin glue and PPF organic matrices were self-forming in situ, but none of these composites were self-setting or self-hardening materials in situ.
Chitosan was admixed in many liquid components of calcium phosphate cement compositions. Chitosan in citric, malic, or phosphoric acid aqueous medium was the liquid component of a self-setting tricalcium phosphate (TCP) or tricalcium phosphate/tetracalcium phosphate (TCP/TTCP) cement (U.S. Pat. Nos. 5,281,404 and 5,180,426). Chitosan in bone cements or substitutes was also studied in the scientific literature, as reported by Leroux et al. (Bone, Vol. 25, No 2, supplement, 1999:31S-34S), Hidaka et al. (J. Biomed. Mat. Res., 46:418-423, 1999), and Ito (Bio-materials, 12:41-45, 1991).
Osteoconduction and osteogenic performances of chitosan based materials were reviewed, and applied to bio-materials development. Chitosan with immobilized polysaccharides such as heparin, heparan sulfate, chondroitin sulfate and dextran sulfate was reported for stimulating hard-tissue regeneration by Hansson et al. (International Patent Publication WO96/02259). Osteoinductive compositions were also developed by admixing hydroxyapatite and bone-derived osteoinductive gelatin to chitosan solutions (U.S. Pat. No. 5,618,339).
The osteoconduction and osteogenic performances of chitosan was also investigated in vitro and in vivo (Hidaka et al., J. Biomed. Mat. Res., 46:418-423, 1999; and Klokkevold et al., J. Periondot., 67:1170-1175, 1996).
It would be highly desirable to be provided with an in situ self-forming mineral-polymer hybrid composition containing genetically-modified MSCs for treating specific hard-tissue deficiencies or diseases such as brittle bone disease, osteoporosis, Paget's diseases, dysplasia, osteogenesis imperfecta, and the like.
It would be highly desirable to be provided with self-forming mineral-polymer hybrid compositions that are applied to substances, defects or cavities of (soft- or hard-) tissues, or to any anatomical structures of tissues, or any body cavities, thus enabling the formation in situ of a group of bio-materials having distinct compositions, functions and properties.